1. Field of the Invention
The present invention relates to track-driven toy vehicles, and more particularly to such vehicles having at least one electric motor that is controlled by radio signals issuing from a hand-held transmitter.
2. Description of the Prior Art
Track-driven toy vehicles are well known in the art. Generally, such vehicles comprise a pair of endless toothed belts, one on each side of the vehicle, which travel about front and rear wheels. French patent No. 499,974 and British patent No. 142,960 show examples of such toy vehicles, in which it will be noted that the diameter of the rear wheels is substantially greater than that of the front wheels.
More recently, radio-controlled track-driven toy vehicles have been introduced on the market by various manufacturers. These toy vehicles typically comprise a pair of independently operable electric motors each of which actuates a rear drive wheel of the vehicle. The rear drive wheels, as well as the front driven wheels of these prior art vehicles, have toothed surfaces, and mesh with the toothed inner surfaces of a pair of endless belts connecting the front and rear wheels on each side of the vehicle.
With particular reference to FIGS. 3 and 4, which show the wheel and track configurations of a conventional such vehicle, the rear wheel 10 is divided by a central annular groove 12 into a pair of radially outwardly extending toothed surfaces each comprising a circular array of teeth 14. Between each pair of adjacent teeth 14 will be found a recess 16 delimiting the teeth. The smooth cylindrical base of the central recess 12 is indicated at 18 in FIG. 3. From this base there rises on each side of groove 12 a radial shoulder 20 that is integral with teeth 14 and recesses 16. According to the prior art construction, this radial shoulder 20 rises only to the base of the recesses 16 and teeth 14.
Rear drive wheel 10 meshes with an endless drive belt 22 that travels about the rear drive wheel 10 and its respective front driven wheel 30 (see FIG. 4). Drive belt 22 has formed on its inwardly-directed surface an endless row of teeth, wherein the side portions 24 of the teeth are substantially shorter than the central portions 26.
It will be appreciated from the above description and the accompanying FIG. 3 that, as belt 22 meshes with and travels about drive wheel 10, the shorter side portions 24 of the belt teeth will be engaged in the recesses 16 between adjacent wheel teeth 14, such that the wheel 10 will drive the belt 22.
On the other hand, the taller central portions 26 of the belt teeth will be received within the central groove 12 of wheel 10. The reception of the taller central portions 26 within groove 12 does not much contribute to the driving of the belt 22 by wheel 10, but rather serves to guide the belt 22 in its travel about wheel 10, and retain the belt 22 in meshing engagement with the wheel 10.
FIG. 4 shows the prior art driven front wheel that is used together with the belt and rear wheel of FIG. 3. The prior art front wheel 30 likewise has a central groove 32 whose width is about the same as that of the central groove 12 of the rear wheel 10. The central groove 32 of front wheel 30 divides the front wheel into two radially outwardly extending annular portions 34. However, unlike the corresponding portions of the rear wheel 10, the annular portions 34 of front wheel 30 are smooth, and have no teeth.
Conversely, the base of groove 32 comprises a circular series of radially outwardly extending teeth 36, unlike the corresponding groove base 18 of rear wheel 10, which is smooth. It will be noted that the radially outwardly extending teeth 36 of front wheel 30 extend between and interconnect the radially extending shoulders 38 defining groove 32.
As the drive belt 22 travels about the front wheel 30, the shorter side portions 24 of the belt teeth contact, but of course do not mesh with, the smooth surfaces 34. Conversely, the taller central portions 26 of the belt teeth are in continuous meshing engagement with the central teeth 36 formed within groove 32.
Thus, the drive arrangement in the prior art toy vehicles of this type provides a positive belt drive at the rear, and similarly a positive belt drive at the front.
In toy vehicles of this type, the power is supplied independently to each of the rear wheels, which power input is variable in both the forward and reverse directions. Accordingly, there is no need to provide for any separate steering of the toy vehicle, as steering is effected by driving. For example, a relatively greater power input to the left rear wheel causes the vehicle to turn toward the right. Similarly, full forward power to the left rear wheel simultaneously with full reverse power to the right rear wheel causes the vehicle to spin like a top in the clockwise direction as viewed from above.